Two-Dimensional Conduction Effects in Estimating Radiative Flux from a Capillary Discharge

Abstract

It is quite common to employ thin metallic films for the determination of heat flux at a fluid-solid interface. Depending on the duration of the event and gage design, it may be important to account for multidimensional heat conduction within the thin-film substrate. Present work investigates the effects of two-dimensional conduction on the deduced radiative heat fluxes using an inverse algorithm. For comparison, a previously developed one-dimensional inverse technique is also used. The high heat fluxes are produced by an electrothermal-chemical plasma jet. The plasma, initiated within a 3.2 mm diameter and 26 mm long polyethylene capillary by exploding a 3.6 mg thin copper wire, emerges into an open-air atmosphere as an underexpanded supersonic jet. The jet impinges over a stagnation plate equipped with thin-film platinum gages, whose temperature history serves as an input to the heat-flux estimation algorithm. Four different charging voltage levels are investigated, ranging from 2.5 to 7.5 kV. While both algorithms capture the temporal variations of the radiative heat fluxes, the two-dimensional model reveals the discrepancies between the two techniques, as well as the range of applicability of the one-dimensional model.